CMP assisted liftoff micropatterning

ABSTRACT

A method and structure for a microelectronic device comprises a first film over a substrate, a first polish resistant layer over the first film, a second film over the first polish resistant layer, a second polish resistant layer over the second film, wherein the first and second polish resistant layers comprise diamond-like carbon. The first film comprises an electrically resistive material, while the second film comprises low resistance conductive material. The first film is an electrical resistor embodied as a magnetic read sensor. The electrically resistive material is sensitive to magnetic fields. The device further comprises a generally vertical junction between the first and second films and a dielectric film abutted to the electrically resistive material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to patterning of microelectronicdevices, and more particularly to CMP assisted liftoff micropatterningof vacuum deposited thin films for microelectronic devices andnanostructures.

2. Description of the Related Art

Patterning materials using photoresists and etching is a technologyknown in the art, which has been advanced by progress inmicroelectronics where structures on the order of 100 nm are used,particularly for very large scale integrated (VLSI) silicon chips andfor magnetic recording heads for computer disk drives. Some vacuumdeposited thin film materials are not easily etched. U.S. Pat. No.3,873,361 issued to Franco et al. teaches that such materials can bepatterned by depositing them through a stencil of photoresist with anoverhanging cross-section. The material within the stencil remains afterthe photoresist is stripped off in a solvent, removing it and theoverlying film. This lift-off process has been used in siliconmicrocircuits and particularly in thin-film recording heads,particularly for defining the magnetoresistive read sensor and itsconductive leads. Creating patterns with gaps smaller than a few hundrednanometers has become exceeding difficult because the depth of theoverhanging structure is limited, and material deposited on the resistforms very undesirable sharp fences when the resist is lifted off. U.S.Pat. No. 5,246,884 issued to Jaso et al. teaches that thin polishresistant layers such as diamond-like carbon (DLC) can be used as agauge layer to stop chemical-mechanical polishing (CMP).

In a liftoff process for attaching electrical leads to a magneticallysensitive resistor (giant magnetoresistive or GMR sensor), one startswith a sensor film which has its dimensions between the leads defined byan ion mill (argon sputter etch) process which removes the GMR sensorwithin the overhanging photoresist opening where the sensor will bedeposited. Then, when the sensor is deposited, using the samephotoresist pattern, the deposited film will be aligned (self-aligned)with the conductive leads deposited into the same photoresist structure.

In the self-aligned process, the ion mill process uses a bi-layer resistwhere the effective photoresist mask is raised off the wafer in order toachieve the necessary undercut, wherein the edge of the sensor has arelatively small angle. Similarly, when the leads are deposited, theytaper as they cover this shallow angle of deposition. This makes theexact length of the GMR sensor difficult to determine and control.

The major problems with the related art are several. First, the liftoffprocess does not scale for sub-micron sized structures of perhaps 250nanometers because the undercut becomes too small. Second, for theexample of very small magnetic read sensors, it is desirable to have theion mill process give steep (nearly vertical) sidewalls so that the readsensor resistors and their self-aligned electrical leads could be welldefined. Such geometry has not been produced by the conventionalprocesses. Finally, the thin polish resistant layers do not clearlyprotect both the deposited film and the previous surface features in theconventional processes. In fact, it is focused on achieving some degreeof planarity. Therefore, there is a need for a new micropatterningtechnique capable of scaling to sub-micron sized devices for materialsthat are difficult to etch.

SUMMARY OF THE INVENTION

The present invention patterns difficult to etch films using aphotoresist pattern similar to that used for a liftoff process. However,the present invention patterns films created with a thin single layer ofphotoresist. The present invention provides a process for creatingfeatures with sub-micron spacing using a new process that builds uponthe previous liftoff process and the use of polish resistant layers toclearly limit the regions covered by the polish process. The presentinvention uses two polish resistant surfaces or films such as very thinlayers of a polish resistant material such as diamond-like carbon. Oneof these films or surfaces is used to protect the surface of the waferoutside of the patterned areas (i.e., under the photoresist) and theother film is used to protect the deposited film from the polishingprocess. During the polishing process, which is used to complete thepatterning, only the very narrow junction between the original surfaceand the deposited pattern is exposed to the polish process, allowing useof topography to help shape and smooth the edges of the patterns.

The process can be used in either an overlay fashion where the depositedfilm is placed directly on top of the existing surface, as in the leadoverlay configuration for magnetic read heads or it can be used in a“self aligned” configuration where an etching process is used to removean underlying film and the deposited film placed in the cavityself-aligned with the edges of the etched film. This is the most commonpractice in defining magnetic read heads where the leads are in the sameplane as the GMR read sensor they contact.

One implementation of the present invention can be illustrated in theexample of the structure for a giant magnetoresistive (GMR) read sensordevice comprising a GMR read sensor with the patterning process creatinggenerally vertical sidewalls for the sensor and two electricalconducting leads connecting to opposite edges of the GMR sensor whichserve as electrical leads and provide the magnetic environment needed bythe sensor. The width of the GMR sensor is one of the key parametersrelated to the density of parallel recording tracks that can be achievedand thus the quantity of information that can be stored by a computerdisk drive. The present invention allows very small GMR sensors to beproduced.

A method of manufacturing a GMR read sensor utilizes a thin film of GMRsensor material deposited on a thin dielectric layer which in turn isdeposited on a magnetic shield which magnetically defines one edge ofthe magnetic read gap. A first thin film of polish resistant materialsuch as diamond-like carbon (DLC) is deposited onto the surface of thewafer to protect the sensor when it is later exposed to a polishingproduct. A thin single layer of photoresist (with or withoutanti-reflection sub-layers) is applied over the polish resistant filmand patterned with openings where the two leads are to be formed and avery narrow line of photoresist between the leads which defines thewidth of the read sensor. The first DLC film is removed from the leadpatterns by a reactive ion etching process (RIE) and the GMR film isetched in the same area using an ion milling process. With the thinsingle-layer of photoresist, a structure having generally vertical wallsof the GMR film can be achieved by ion milling, which is a structuralfeature achieved by the invention.

The thin film leads are now vacuum deposited over the entire wafer.These leads are comprised of a magnetic bias layer to provide theappropriate magnetic environment for the GMR film and highly conductivelayers. The leads fill the patterns in the photoresist where they areneeded, but also cover the photoresist. A second polish resistant film(such as DLC) is deposited over the lead film in order to protect itwithin the lead pattern areas. The photoresist and the portion of thethin film leads overlying it can be removed by a conventionalthermal/chemical strip. In some cases this process is optional becausemany photoresists are weak enough mechanically to be removed bypolishing. The structure is then subject to a chemical-mechanicalpolishing process in which only the narrow margin surrounding the leadpatterns are affected by the process. The resistant films over the leadsand GMR sensor protect those two areas. Thickness differences betweenthe leads and the sensor determine the shape of the junction between thetwo areas. The leads, being generally thicker will be gradually roundedas the resistant layer erodes from the edges while the sensor remainsfully protected.

In an alternate configuration, the definition of the read sensor stripand the bias layer is accomplished separately from the deposition of theleads. Because the sensor is larger in this configuration, conventionalliftoff processes may be used to pattern the read sensor and the biaslayer. The leads are then deposited on top of the GMR sensor rather thanabutted as above. This lead overlay (LOL) process is essentially thesame as that above except that the ion milling step is not used. Thelead overlay process is particularly challenging since the spacingbetween the leads is significantly smaller than the functionalread-width of the head. The required spacing can be roughly half theread width, requiring a 0.07 micron spacing between leads in order toachieve a read track of 0.15 microns.

A third configuration is used to define the backside of the read sensor.This is similar to the first, but an insulator is used to abut thesensor after ion milling rather than metallic leads. The ion millprocess defines a generally vertical wall on the GMR sensor thin film.Alumina or an equivalent insulating material is then deposited over thephotoresist sealing the back side of the sensor and defining itprecisely. This fill is generally near the same thickness as the GMRfilm such that the result after polishing is a near-planar junction.

The invention provides a patterning process for vacuum deposited thinfilms utilizing two polish resistant layers or material surfaces and aCMP polish to remove unwanted material, called fences, from thedeposition process, and allow the CMP to be used to tailor the profilesof the junction between the deposited film and the surrounding areas.When it is used with ion milling to produce abutted structures, theclose masking permits generally vertical interfaces between the originalpatterned surface and the abutted deposited film.

While the three examples given are related to the manufacturing processfor read sensors for thin film recording heads, it is clear that theinvention is useful in many other areas such as silicon microelectronics(where new thin film materials can be accommodated), nanostructures suchas attachment of leads to very small elements, and micromechanicalsystems.

The invention provides a microelectronic device comprising a first filmover a substrate, a first polish resistant layer over the first film, asecond film over the first polish resistant layer, a second polishresistant layer over the second film, wherein the first and secondpolish resistant layers comprise diamond-like carbon. The first filmcomprises an electrically resistive material, while the second filmcomprises low resistance conductive material. The first film is anelectrical resistor embodied as a magnetic read sensor. The electricallyresistive material is sensitive to magnetic fields. The device furthercomprises a generally vertical junction between the first and secondfilms and a dielectric film abutted to the electrically resistivematerial.

The invention further provides a magnetic sensor device comprising aread sensor, and an electrical lead having a generally vertical sidewallconnecting to the read sensor, wherein the read sensor comprises a giantmagnetoresistive insulator film. The electrical lead comprises amagnetoconductive film, and the magnetoconductive film comprises amagnetic bias film and a conductive lead film.

An advantage of the present invention is that by using appropriatepolish resistant layers and topography selections, a film deposited ontop of a photolithographic image can have the material overlying theresist removed along with the resist film using a polishing process.This allows patterning of difficult to etch film materials moreprecisely and enables production of a smaller feature size than could beobtained by previous processes such as stencil liftoff which requiresoverhanging lithographic structures. Furthermore, the present inventionprovides a new liftoff-like process that uses polish resistant layersand polishing to allow difficult to etch materials to be patterned withgaps significantly smaller than can be reliably achieved by theconventional liftoff process. Additionally, while the conventionalprocesses are focused on achieving some degree of planarity, the presentinvention involves structures which may be distinctly non-planar.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following detaileddescription of a preferred embodiment(s) of the invention with referenceto the drawings, in which:

FIG. 1 is a schematic diagram of a partially completed microelectronicdevice undergoing micropatterning;

FIG. 2 is a schematic diagram of a completed microelectronic deviceundergoing micropatterning;

FIG. 3 is a schematic diagram of an alternate embodiment of a completedmicroelectronic device undergoing micropatterning;

FIG. 4 is a schematic diagram of a partially completed microelectronicdevice undergoing micropatterning;

FIG. 5 is a schematic diagram of a partially completed microelectronicdevice undergoing micropatterning;

FIG. 6 is a schematic diagram of a partially completed microelectronicdevice undergoing micropatterning;

FIG. 7 is a schematic diagram of a partially completed microelectronicdevice undergoing micropatterning;

FIG. 8 is a schematic diagram of a partially completed microelectronicdevice undergoing micropatterning;

FIG. 9 is a schematic diagram of a partially completed microelectronicdevice undergoing micropatterning;

FIG. 10 is a schematic diagram of a partially completed microelectronicdevice undergoing micropatterning;

FIG. 11 is a schematic diagram of a partially completed microelectronicdevice undergoing micropatterning;

FIG. 12 is a schematic diagram of a partially completed microelectronicdevice undergoing micropatterning;

FIG. 13 is a schematic diagram of a completed microelectronic device;

FIG. 14 is a flow diagram illustrating a preferred method of theinvention;

FIG. 15 is a schematic diagram of an alternative embodiment of apartially completed microelectronic device undergoing micropatterning;

FIG. 16 is a schematic diagram of an alternative embodiment of apartially completed microelectronic device undergoing micropatterning;

FIG. 17 is a schematic diagram of an alternative embodiment of apartially completed microelectronic device undergoing micropatterning;

FIG. 18 is a schematic diagram of an alternative embodiment of apartially completed microelectronic device undergoing micropatterning;

FIG. 19 is a schematic diagram of an alternative embodiment of apartially completed microelectronic device undergoing micropatterning;

FIG. 20 is a schematic diagram of an alternative embodiment of apartially completed microelectronic device undergoing micropatterning;

FIG. 21 is a schematic diagram of an alternative embodiment of acompleted microelectronic device;

FIG. 22 is a flow diagram illustrating an alternate method of theinvention;

FIG. 23 is a schematic illustration by transmission electron microscopy(TEM) of a magnetoresistive sensor between two leads as produced byconventional lift-off techniques;

FIG. 24 is a schematic illustration by transmission electron microscopy(TEM) of a magnetoresistive sensor between two leads as produced by thepresent invention; and

FIG. 25 is a flow diagram illustrating a preferred method of theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

As previously mentioned, there is a need for a new micropatterningtechnique capable of scaling to sub-micron sized devices for materialsthat are difficult to etch. A good example of this need is thedefinition of the magnetic read sensor for the recording head of a highcapacity computer disk drive. The read sensor is a small magneticallysensitive electrical resistor utilizing the giant magnetoresistiveeffect. In order to achieve a recording density in the order of 50gigabits/in² there would need to be approximately 1×10⁵ circularrecording tracks per inch on the disk, allowing a spacing of 250 nm permagnetically written track. The read sensor should be significantlynarrower than the track spacing, so that a read sensor width of 100-150nm is used with increasing demands as recording technology advances.This read sensitivity is controlled by the spacing between the twoelectrical leads which connect to the sensor.

Referring now to the drawings and in particular to FIGS. 1 through 22and FIGS. 24 through 25, there are shown the preferred embodiments ofthe present invention. While there are many potential applications forthe process of the present invention in microelectronics andnanotechnology, examples related to defining the tiny giantmagnetoresistive (GMR) read sensor for a recording head will be used toillustrate the process and its capabilities.

The present invention will be described in terms of the fabrication ofelectrical conducting leads for the magnetic read sensor of a thin-filmrecording head. This is a convenient example since it can be used eitherto inset abutted leads, self-aligned to the read sensor or it can beused to overlay the leads onto the surface of the read sensor. Both ofthese embodiments are examples of the use of the new patterning processprovided by the present invention.

In these examples, the polish resistant surface is achieved by using athin layer of diamond-like carbon applied over an adhesion layer ofsilicon. Accordingly, approximately 5-20 nm of DLC over approximately0.5-2 nm of silicon provides a very durable surface coating with anextremely low erosion rate when polished with soft abrasives such ascolloidal silica. Clearly many other combinations of polish resistantsurfaces and abrasives can be substituted, with the principle being thatthe erosion rate of the surface in the polishing should to be minimal.This polish resistance is combined with the use of topography to directthe majority of the polishing to one side or another of the leadjunction.

The preferred embodiment of the present invention uses a selective CMPprocess for lithographically defined patterning of thin film materialswhich are difficult or impossible to pattern using an etching process.The present invention teaches a process which makes use of a thinsingle-layer photoresist pattern and, through the use of selectivepolish resistant surfaces, achieves the removal of the photoresist andoverlying thin film via a polishing process.

FIG. 1 shows a sketch of a wafer surface view of a read sensor for amagnetic recording head 65 abutted to two conductive leads 55. The widthof the read sensitivity is defined by the spacing between the two leads55. One embodiment of this invention is to pattern these leads 55 whichare a composite film, and which are difficult to etch. In buildingrecording heads, this patterning has been conventionally performed by astencil lift-off process which requires an overhanging photoresistprofile, usually achieved using a bi-layer resist. However, thisconventional process grows increasingly difficult for patterns underseveral hundred nanometers, such as a GMR device. The two embodimentsdescribed according to the present invention are applicable tosignificantly smaller dimensions because they can be defined using athin single-layer photoresist along with lithographic enhancements suchas deep UV exposure with phase mask techniques or electron beamexposure.

After the read sensor 65 and leads 55 are positioned, an electromagneticwrite head will be fabricated in layers on top of the read head. Whenthe wafer processing is completed, the individual heads will be cut out(shown as dotted line in FIG. 1) of the wafer and lapped on a surfaceperpendicular to an air bearing surface 11. It is this surface whichfaces the rotating disk. The preferred embodiments are best illustratedby looking at the structural cross-section at the air bearing surface 11described below.

FIG. 2 shows a preferred embodiment of the read head sensor 65 viewed asa cross-section at the air bearing surface 11. As shown, the read sensor65 is abutted to the conductive leads 55. The sensor 65 and leads 55 areplaced between two soft magnetic shields 5, 10. The spacing between thetwo shields 5, 10 defines the spatial resolution of the sensor 65 alongthe recording track (not shown). Because the shields 5, 10 areconductive, the sensor 65 and leads 55 are insulated from the shields 5,10 by a thin dielectric layer 3.

To achieve a linear recording of 5×10⁵ bits per inch, the read sensor 65is sensitive to magnetic transitions on the order of 50 nm apart. Thespacing of the shields 5, 10 determines the zone of sensitivity and thespacing between shields 5, 10 is preferably on the order of 50 nm in thevicinity of the sensor 65. Thus, the combined thickness of the sensor 65and the insulating film 3 above and below the sensor 65 is preferablyvery small. As shown, the leads 55 are generally somewhat thicker thanthe sensor 65 in order to keep their electrical resistance smallcompared to the resistance of the GMR sensor 65.

FIG. 3 shows an alternate embodiment in which the leads 155 are overlaidon top of the sensor film 165. In this configuration, the sensor 165utilizes separate bias magnets 175 abutted to the ends of the sensor165. Like the preferred embodiment, the overlay structure includesmagnetic layers 110 and 105 and a dielectric layer 13 disposedtherebetween. Because the sensor 165 is larger than the critical spacingbetween the leads 155, the patterning of the bias magnets 175 and sensor165 is less critical and can be accomplished with either the CMPassisted process of the present invention or with a conventionallift-off process. While the alternative configuration (FIG. 3) of theleads 155 is generally more simple than for the abutted configuration(FIGS. 1 and 2 ), the process is challenging because the sensitiveregion of the GMR sensor 65 is somewhat wider than the lead spacing andspacing between leads 55 under 100 nm may be required.

FIGS. 4 through 14 illustrate the process in further detail (all showingthe cross-sectional view at the air bearing surface 11). While alternateprocess sequences can be practiced, FIG. 4 shows a small region of theGMR sensor film 65 which has been patterned by an ion mill process whichetches the sensor film 65 away except in the region 4 where the leadsare to be defined. A dielectric material 3 such as alumina is thendeposited around the etched sensor region 4, which fills the area wherethe sensor 65 is removed and brings the surface back to an essentiallyplanar condition. This patterning can be performed by using either aconventional lift-off process or by the CMP assisted technique of thepresent invention. As shown in FIG. 4, the thin dielectric layer 3 lieson the lower magnetic shield 10.

Next, as shown in FIG. 5, in order to protect the sensor 65 andsurrounding areas from the polishing step occurring later in theprocess, a polish-resistant film 30 is applied on top of the sensor 65and dielectric layer 3. Several different types of thin films 30 may beused, including a diamond-like carbon (DLC) film that is essentiallyequivalent to the films used on the head air bearing surface and therecording media for tribology and wear resistance. For illustrativepurposes, the remainder of the process will be described using a DLCfilm as the polish-resistant film 30. Preferably, the parameters of thepolish resistant film 30 includes 10 nm of DLC on top of a 1 nm siliconadhesion layer (the individual layers are not shown in the drawings, butrather collectively form the polish resistant film layer 30).

Other parameters of the polish resistant film 30 includes a polishresistant surface in which the removal rate by polishing flat surfaces(without topography) is small compared to the polish erosion rate ofother materials exposed to edges where the polish process is enhanced bytopography. This property can be controlled by the physical/chemicalproperties of the surface, the hardness of the polishing abrasives, andthe chemistry in the polishing environment. Attributes which create goodpolish resistance includes a surface with a physical hardness greaterthan that of the abrasive, wherein silicon carbide, tantalum nitride,boron carbide, and diamond-like carbon are materials that are harderthan abrasives such as colloidal silica. Other attributes include asurface which is tough and/or ductile so that it is not removed by theabrasive. Such surfaces may be soft, rather than hard, and includematerials such as copper, rhodium, and nylon. Still other attributesinclude a surface with a low coefficient of friction, such asdiamond-like carbon; and using a softer abrasive (ceria, rouge, andsilica are soft, as compared to alumina, silicon carbide, and diamondwhich are not as soft). Finally, chemistry can play an important rolealso. For example, copper is polish resistant in some chemistries andeasily polished in others, while diamond-like carbon is inert in mostchemical environments.

As further illustrated in FIG. 5, a photoresist film 40 is applied overthe DLC layer 30 and patterned with open areas 32 where the leads willbe placed. The feature that will define the read sensor 65 is the narrowresist pattern 41 between the open areas 32. The resist pattern 41comprises the photoresist film 40. This narrow resist pattern 41preferably has a width of 100 nm or less. The lithography process may ormay not use an anti-reflection layer, and the pattern definition isconventional, but has a very high resolution.

Next, a reactive ion etch (RIE) process is used to etch through the DLClayer 30 in the open areas 32 as shown in FIG. 6. Because the DLC layer30 is quite thin, the erosion of the resist 40 by the RIE process issmall. The RIE process exposes the GMR sensor material 65 and itssurrounding alumina insulator 3 except for the zone underneath theresist pattern 41. Both the GMR sensor 65 and the alumina insulator 3comprise materials which are very difficult to etch.

FIG. 7 shows the structure after an ion mill process in which thesurface of the wafer 1 is bombarded with energetic argon ions to sputteraway the read sensor 65 and surrounding alumina 3. The photoresist 40and DLC film 30 protect the surface of the wafer 1 except where theleads are to be placed in open areas 32. This process is terminated whenthe sensor 65 has been adequately removed with very little loss ofthickness of the alumina insulator 3 in the area 32 where the leads willbe placed.

Next, FIG. 8 shows the preferred embodiment after deposition of aconductive lead layer 55. The lead layer 55 comprises a multi-layer filmwith a bottom layer (not shown) which contains a permanent magnet filmto keep the read sensor 65 correctly magnetically oriented and aconductive top layer (not shown) for connecting to the GMR read sensor65. The lead layer 55 completely covers the open areas 32 (previouslyshown in FIG. 7) and the photoresist 40 as well as any exposed surfacesof the DLC film 30, but the lead layer 55 specifically touches bothsides of the GMR sensor 65 making the critical electrical connection andcreating the appropriate magnetic environment.

In order to provide protection of the leads in the subsequent polishingprocess a second polish resistant layer 31 is placed on top of the leadlayer 55, which is illustrated in FIG. 9. If the top of the lead metal55 were sufficiently polish resistant, then this step would not benecessary. This second polish resistant layer 31 may, for example, beidentical to the first polish resistant layer 30. Moreover, the secondpolish resistant layer 31 may comprise DLC, and specifically comprisesapproximately 10 nm of DLC deposited on a 1 nm silicon adhesion layer(shown collectively as layer 31).

In the preferred embodiment of the present invention, the photoresist 40may be removed in an optional chemical stripping process. This processgenerally involves a bake to “wrinkle” the resist followed by a chemicalstripping that removes the photoresist 40 and the materials overlyingit, such as portions of the lead layer 55 and second DLC layer 31. FIG.10 illustrates the structure after the photoresist 40 is removed. Asshown, the second DLC layer 31 and lead metal 55 that coated the sidesof the photoresist 40 is sheared and leaves major protrusions or fences99. Nonetheless, the leads 55 remain covered with the second polishresistant layer 31. Moreover, the sensor 65 and the insulator 3surrounding the leads 55 are covered by the first polish resistant layer30. Additionally, only the very rough edges 99 of the leads 55 areunprotected by a polish resistant surface.

The wafer 1 is now subject to a CMP step. In this step, the wafer 1 ispolished with a soft abrasive in a slurry (or embedded in a polishingpad) according to conventional CMP processes used in themicroelectronics industry. A relatively soft abrasive such as colloidalsilica is used in order to polish the soft metal material of the leads55 without significantly affecting the polish resistant layers 30, 31.

FIG. 11 illustrates the results of the polishing process, wherein thefences 99 are polished away. By using the topography of leads 55 whichare slightly thicker than the GMR sensor 65, the polishing isconcentrated on the edges 95 of the leads 55 where the polish resistantfilm 31 is slowly eroded from the edge 95 producing a smooth, fence-freecontour.

FIG. 12 shows the preferred embodiment after removal of the polishresistant layers 30, 31 with a RIE process. A second dielectric layer15, preferably alumina is then deposited on the surface of the wafer 1.Next, a second magnetic shield 5 deposited and patterned over the wafer1, and the completed device 100 results in the structure shown in FIG.13 with the leads 55 self-aligned and abutted to the GMR sensor 65.

FIG. 14 outlines the process flow for the preferred embodiment ofmanufacturing abutted leads. As indicated, the process begins 405 witheither a full-film GMR sensor 65 on a thin dielectric layer 3 over amagnetic shield 10 or a patterned GMR sensor 65 inset on an insulatingfilm 3. Next, a thin polish resistant film 30, such as DLC, is deposited410 on the wafer 1 and a photoresist film 40 is spun on and patternedfor defining the two subsequent conductive leads with the GMR sensor 65defined therebetween. Then, the polish resistant film 30 is patterned415 using a RIE process. After this, the GMR film 65 and the surroundinginsulator film 3 are etched 420 by an ion milling process, which thendefines the narrow GMR sensor 65 between the lead cavities 32.

The next step involves depositing 425 a bi-layer lead material 55comprising a magnetic bias layer with a conductive layer on top. Thisprocess fills the cavities 32 for the resulting leads 55 and covers thewafer 1. Next, a second polish resistant layer 31, such as DLC, isdeposited 430 over the wafer 1. Thereafter, the photoresist 40 andsecond polish resistant film 31 and lead layer 55 overlying thephotoresists 40 are removed 435 by either chemical stripping or by useof a CMP process. The stripping process leaves severe fencing 99 of thelead material 55 deposited on the resist sidewalls 40. In the next stepof the process, a CMP process is used to remove 440 the fences 99. Here,the leads 55, GMR sensor 65, and surface of the wafer 1 are protected bythe polish resistant films 30, 31. The polishing process also smoothesthe perimeter 95 of the leads 55. Moreover, the topography of the leads55 along with the first DLC layer 30 protect the sensor 65. Next, thepolish resistant films 30, 31 are removed 445 using a RIE process.Finally, a top insulating layer 15 and a second magnetic shield 5 aredeposited 450 on top of the wafer 1 to complete the sensor device 100.

FIGS. 15 through 22 illustrate an alternate embodiment with overlaidleads 155 rather than the abutted leads 55 of in FIGS. 4 through 14).The alternative embodiment offers some potential for improvedsensitivity of the read sensor 165, but with the need for the spacingbetween the leads 155 to be significantly smaller than the read trackwidth. To match the track width of an abutted read sensor with 150 nmspacing between leads, an overlaid structure uses spacing ofapproximately 70 nm. The present invention achieves this by using theprocess described below.

As shown in FIG. 15, a protective DLC film 130 and photoresist film 140is used to define the open areas 132 where the leads will be formed. Thestructure is similar to the abutted structure of the preferredembodiment, wherein a dielectric layer 13, preferably comprisingalumina, is provided above a magnetic shield 110. Moreover, the resistpattern 141 is used to define the resulting leads 155. Also, asindicated in FIG. 15, the DLC 130 is patterned to expose the sensor 165and bias magnets 175. Furthermore, in the alternative configuration, themagnetic bias layer 175 is produced separately from the leads 155 ratherthan being a sub-layer within the leads 155. The read sensor 165 isphysically larger with the magnetic bias layer 175 abutting it andrefilled to planarity as shown in FIG. 16. Because the dimensions can belarger, the starting structure can be fabricated using either aconventional lift-off patterning technique or the CMP assisted processof the present invention.

In the case of the overlaid leads of the alternate embodiment, the GMRfilm 165 is not ion milled as in the preferred embodiment. Instead, theconductive lead layer 155 (without a need for a magnetic sub-layer) isdeposited over the wafer 11 as shown in FIG. 16.

Again, a second polish resistant film 131, preferably comprising DLC, isapplied over the conductive lead layer 155 as illustrated in FIG. 17.The photoresist 140 is removed by chemical stripping as in the previousexample, which results in the structure illustrated in FIG. 18, leavingfencing 199 at the edges 195 of the conductive leads 155 similar tothose of the abutted pattern in the preferred embodiment.

Thereafter, a CMP polish using a generally soft abrasive is used toremove the fences 199 and to provide a smooth contour to the conductiveleads 155 as shown in FIG. 19. Next, the polish resistant films 130, 131are removed by a RIE process, with the resulting structure illustratedin FIG. 20.

Then, a capping insulating layer 115 is applied over the dielectriclayer 13 as well as the sensor 165 and leads 155. After which, a secondmagnetic shield 105 is deposited and patterned completing the sensordevice 101 with overlaid leads 155 as shown in FIG. 21. FIG. 22 is aflow diagram illustrating the alternative embodiment, wherein theprocess begins on a GMR sensor film 165 with bias layers in place. Athin polish resistant layer 130 is deposited 505 on the sensor film 165,and subsequently, a photoresist film 140 and the polish resistant layer130 are patterned by RIE for defining the areas 132 where the subsequentleads 155 will be formed. Next, the conductive lead layer 510 isdeposited without etching a cavity so that the leads 155 are placed overthe GMR sensor 165 thereby producing a lead overlay configuration. Then,a second polish resistant layer 131, preferably comprising DLC, isdeposited 515 over the wafer 1. In the next step of the process, thephotoresist 140 and films overlying it (portions of the lead layer 155and second polish resistant layer 131) are removed 520 by eitherchemical stripping or by use of a CMP process. The stripping processleaves fencing 199 of lead material 155 deposited on the resistsidewalls 140.

In the next step, a CMP process is used to remove 525 the fences 199.Here, the leads 155, GMR sensor 165, and dielectric surface 13 areprotected by the remaining polish resistant layers 130, 131. Also, inthe polishing step, the perimeter of the leads 155 are smoothed with thetopography of the leads 155 and the first DLC layer 130 protecting thesensor 165. Thereafter, the remaining polish resistant films 130, 131are removed 530 with a RIE process, and finally, a top insulating layer115 and second magnetic shield 105 are deposited 535 to complete thesensor device 101.

When CMP assisted polishing is used to create abutted leads 55 to a readsensor 65 as described in the first embodiment, many advantages ariseover the conventional devices and processes. With the conventionallift-off process where the shadowing resist structure is raised off thesurface of the GMR film, the ion milled edges of the film are sloped asshown in the junction profile of FIG. 23. This makes the length of themagnetic sensor region generally indeterminate and very sensitive to theion mill process. With the CMP assisted process of the presentinvention, the sensor edges 56 (shown in FIG. 2) are near vertical,making a superior structure for precisely defining the size of the GMRsensor 65. The GMR sensor 65 with near vertical walls between it and theleads 55 is shown in the junction profile of FIG. 24.

Similarly, with the back edge of the read structure 65 between the twoleads 55, when this is defined by a conventional lift-off process, theion mill process produces a gradually sloped structure, part of which iselectronically inactive when subject to varying magnetic fields.However, when this edge is defined with the CMP assisted process of thepresent invention, its profile is generally vertical and there is not along tail of inactive material shunting the sensor electrically.

When CMP assisted lift-off is used in an overlay fashion, as shown inthe second embodiment of the present invention, the challenges are toproduce the very small spacing between the leads 155 without fencing199. The CMP assisted process removes all fences 199 in the polishingprocess and, using a thin single-layer photoresist 140, is capable ofproducing leads 155 on the top of the sensor 165 with spacing under 100nm. In this size range, the conventional lift-off process simply cannothave enough undercut to avoid fencing.

Generally, a method for patterning a microelectronic device isillustrated in the flow diagram of FIG. 25, wherein the method comprisesdepositing 605 a first film 65 on a substrate (not shown); positioning610 a stencil 40 over the first film 65; depositing 615 a second film 55over the stencil 40; removing 620 the stencil 40 and the second film 55overlying the stencil 40; and polishing 625 the first and second films65, 55 to remove sidewall fences 99 and to smoothly shape the first andsecond films 65, 55. The stencil 40 used in the process is a photoresiststencil 40. Alternatively, the stencil 40 comprises a material createdby a photolithographic image transfer process.

The first and second films 65, 55 may comprise polish resistantmaterials comprising diamond-like carbon. Also, a polish resistant film30, 31 is deposited on the first and second films 65, 55, respectively,wherein the polish resistant film 30, 31 comprises diamond-like carbon.Furthermore, the polish resistant film 30, 31 is deposited by a vacuumdeposition process, wherein the vacuum deposition process comprisessputter deposition, chemical vapor deposition, evaporation, and ion beamdeposition. Moreover, the polish resistant film 30, 31 are selectivelypatterned using any of reactive ion etching, plasma processing, andchemical etching techniques. In the step of removing 620, the stencil 40and the second film 55 overlying the stencil 40 are removed byperforming a thermal and chemical stripping process. Alternatively, inthe step of removing 620, the stencil 40 and the second film 55overlying the stencil 40 are removed during the polishing step 625.

Several other embodiments exist for the present invention. For example,many other films can be used and patterned using the above techniques.In particular, any film that is patterned using a conventional stencillift-off process is likely to be converted to the CMP assisted processas lithographic dimensions decrease. Additionally, in fabricatingrecording heads, the CMP assisted patterning described above may be usedfor patterning metals, alumina, bias layers, etc. Moreover, while ionmilling is used to etch the GMR film for the abutted embodiment, a RIEprocess may be used depending upon the type of material selected for theGMR film. For example, materials which are more suitable to etching acavity for self-aligned applications would preferably use an RIFprocess.

Additionally, the present invention is a potential alternate todamascene processes used for leads in silicon integrated circuittechnology. Furthermore, the ability to create very small patterns indifficult to etch materials may broaden opportunities for new materialusage in microelectronics generally. Moreover, while chemical strippingof the photoresist is included in the preferred embodiments, somephotoresists have mechanical properties that make this step unnecessary.Also, the photoresist and overlying films can be removed in the samepolishing step that smoothes the surface and removes fences.

An advantage of the present invention is that by using appropriatepolish resistant layers and topography selections, a film deposited ontop of a photolithographic image can have the material overlying theresist removed along with the resist film using a polishing process.This allows patterning of difficult to etch film materials moreprecisely and enables production of a smaller feature size than could beobtained by previous processes such as stencil liftoff which requiresoverhanging lithographic structures. Furthermore, the present inventionprovides a new liftoff-like process that uses polish resistant layersand polishing to allow difficult to etch materials to be patterned withgaps significantly smaller than can be reliably achieved by theconventional liftoff process. Additionally, while the conventionalprocesses are focused on achieving some degree of planarity, the presentinvention involves structures which may be distinctly non-planar.

While the invention has been described in terms of preferredembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theappended claims. While the present invention provides a generalpatterning process for thin films using a single layer resist, polishresistant thin films or surfaces, selective polishing, and topographyeffects. As mentioned, there are many potential applications for theprocess of the present invention in microelectronics and nanotechnology.For example, the present invention may be applicable for creatingself-aligned leads for a GMR sensor. It can be used to overlay leads ona GMR sensor (lead overlay). It can be used to define the back side ofthe read sensor and re-planarize the surface with an alumina dielectricfilm. It can be used anywhere one might use liftoff to avoid fencing. Itmay also be used in silicon microchip manufacturing. It will also findother applications in fabricating magnetic recording heads, in siliconmicroelectronics and microelectromechanical (MEM) technology, and innanotechnology. Furthermore, the patterning process of the presentinvention is not limited to the use of organic resist layer masks forsensor definition. For example, hard masks such as SiO₂ or TaO_(x) canalso be lifted off if they are supported by a thin (a few hundred ofangstroms) organic layer.

1. A microelectronic device comprising: a first film over a substrate; afirst polish resistant layer over said first film; a second film oversaid first polish resistant layer; a second polish resistant layer oversaid second film; and a generally vertical junction between said firstand second films, wherein said first and second polish resistant layerscomprise diamond-like carbon.
 2. The device of claim 1, wherein saidfirst film comprises an electrically resistive material.
 3. The deviceof claim 2, wherein said electrically resistive material is sensitive tomagnetic fields.
 4. The device of claim 2, further comprising adielectric film abutted to said electrically resistive material.
 5. Thedevice of claim 1, wherein said second film comprises low resistanceconductive material.
 6. The device of claim 1, wherein said first filmis an electrical resistor.
 7. The device of claim 6, wherein saidelectrical resistor is a magnetic read sensor.
 8. A magnetic sensordevice comprising: a read sensor comprising polish resistant materials;and an electrical lead having a generally vertical sidewall connectingto said read sensor, said electrical lead comprising polish resistantmaterials, wherein said read sensor comprises a giant magnetoresistiveinsulator film, and wherein said polish resistant materials comprisediamond-like carbon.
 9. The device of claim 8, further comprisingmagnetic shields surrounding said read sensor and said electrical lead.10. The device of claim 9, further comprising a dielectric layerseparating said magnetic shields from said read sensor and saidelectrical lead.
 11. The device of claim 8, further comprising a magnetabutting said read sensor.
 12. The device of claim 8, further comprisinga write head adjacent to said read sensor.
 13. A magnetic sensor devicecomprising: a read head comprising polish resistant materials; a writehead adjacent to said read head; and a plurality of electrical leadscomprising polish resistant materials, and a generally vertical sidewallconnecting to said read head, wherein said polish resistant materialscomprise diamond-like carbon.
 14. The device of claim 13, wherein saidelectrical leads comprise a magnetoconductive film.
 15. The device ofclaim 13, wherein said magnetoconductive film comprises a magnetic biasfilm and a conductive lead film.
 16. A magnetic sensor devicecomprising: a read head comprising polish resistant materials; andelectrical leads having a generally vertical sidewall connecting to saidread head, said electrical leads comprising polish resistant materials,wherein said read head comprises a giant magnetoresistive insulatorfilm, and wherein said polish resistant materials comprise diamond-likecarbon.
 17. The device of claim 16, further comprising magnetic shieldssurrounding said read head and said electrical leads.
 18. The device ofclaim 17, further comprising a dielectric layer separating said magneticshields from said read head and said electrical leads.